1. The Field of the Invention
The present invention relates to pressure vessels for carrying pressurized fluids. More specifically, the present invention relates to tanks designed to support an external, compressive load as well as the pressure of the fluid, for use in applications in which lightweight storage and structural members are desirable.
2. The Relevant Technology
Pressure vessels, or storage tanks, are commonly used to store fluids under pressure. Many types of propulsion vehicles require some type of fluid storage. For example, many types of launch vehicles, spacecraft, missiles, satellites, and rocket-propelled torpedoes all store a fluid propellant. Liquid fuel rocket motors typically require tanks of pressurized, combustible fluids that can be combusted and ejected from a nozzle to propel the rocket. Many forms of electric propulsion also require a pressurized fluid propellant. The term xe2x80x9cfluidxe2x80x9d includes both gases and liquids; many rockets store fuels in a substantially liquid form, with a component of combustible vapor. Additionally, rockets have a number of other structural features necessary for the rocket""s operation. For example, rockets may have additional tanks, nozzles to direct exhaust gases, and thrust structures designed to convey force from the nozzle to the main body of the rocket. Typically, the inside of a rocket is a mass of tubes, tanks, wiring, and fixtures.
The cost and performance requirements that rockets typically operate under frequently dictate the use of lightweight, compact components. As a result, it is desirable to minimize mass and eliminate as much unnecessary structure as possible. Many vehicle applications are also volume sensitive and require that wasted space within the vehicle be minimized wherever possible. Tanks known in the art, however, are not well-suited to compact assembly, in part because they are often shaped with symmetrical, convex walls. Consequently, space between independent tanks and requisite inter-tank structure is typical. Furthermore, tanks known in the art create an enormous blockage through which it is difficult to route wiring, plumbing, conduits, and structural features necessary for operation of the rocket. The complexity of the rocket design is compounded because every other component of the rocket must be designed around the tank.
Furthermore, rockets often contain multiple tanks to hold different fluids, such as an oxidizer and a fuel. For example, oxygen may be stored in one tank, and a suitable liquid fuel in the other, so that the two may be combined to combust even in a vacuum. The use of multiple tanks adds additional complexity, volume, and weight to the rocket. A liquid-fueled rocket must typically carry two tanks, even though the fluids contained in the tanks are stored at similar pressures and will often be routed to the same location.
Consequently, there is a need, unfulfilled by the prior art, for part count reduction and for space and weight conserving tankage that can be effectively positioned within the body of a rocket or a similar propulsion vehicle, without hindering the placement of necessary equipment. There is a further need for space-saving configurations and structures that can be effectively used with tankage for the vehicle. The tankage and structures should be easily manufactured at low expense, and easy to assemble. Furthermore, the tankage and structures should be sturdy enough to tolerate the stresses created by high acceleration and vibration.
Similarly, there is a need for novel methods of manufacture, through which improved tankage and structures can be created, assembled, and installed in a propulsion vehicle. Such methods should be rapid, inexpensive, and preferably utilize available tooling with little modification.
The current invention discloses such an apparatus and method.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available tankage and propulsion vehicle structures. Thus, it is an overall objective of the present invention to provide tankage and propulsion vehicle structures that overcome the deficiencies in the prior art.
To achieve the foregoing objective, and in accordance with the invention as embodied and broadly described herein in the preferred embodiment, integrated tankage for propulsion vehicles and the like is provided. The integrated tankage comprises a wall, or pressurized membrane, at least a portion of which is specifically engineered to serve a function besides containment of the fluid within the tank.
For example, a thrust structure for a propulsion vehicle connects the engine to the main body of the rocket. When the rocket ignites, the engine pushes the rocket forward, and the thrust structure must bear the compressive stress induced by the force of the engine. The engine typically terminates, at its lower (aft) end, in an orifice, or nozzle, through which exhaust gases may pass to propel the rocket. The thrust structure connects the engine to the main body of the rocket, which is typically a cylindrical outer housing. The thrust structure is specially designed to support all engine loads while minimizing weight and bulk.
A tank may be properly situated and constructed to connect the nozzle with the main body of the rocket, such that a separate, thrust structure external to the tank is not necessary. The outer pressurized membrane of the tank may be configured so as to transfer the compressive force of the engine to the body, or an inner, tubular and/or conical structure within the tank may be connected to the nozzle to carry the compressive force. If a tank-internal structure penetrates the pressurized membrane of the tank, the two structures may be mechanically uncoupled, and a compliant liner or seal such as an O-ring seal or rod packing may be used at their juncture in such a way that the two structures may deform at different rates without leakage of internal fluid.
In the alternative, the engine itself may be integrated with the tank, such that the lower (aft) end of the tank is shaped to form a nozzle. In such a configuration, the pressure of expanding exhaust gases in the nozzle would impinge directly on the aft pressurized membrane of the tank, so that the tank supports the nozzle. A separate thrust structure may then be provided to connect the engine to the main body of the rocket, or the tank may also transmit the force of the engine directly, thus enabling integration of both the engine and the thrust structure into the tank. The nozzle may be of a conventional type, or may have an annular, xe2x80x9caerospikexe2x80x9d design. A compliant liner or seal between the engine or thrust structure and outer pressurized membrane may be employed to permit varying rates of strain, as described above.
As a further alternative, a tank may have an internal wall adapted to form a bulkhead between nested internal chambers, thereby merging abutting pressure vessels to form a single lighter, simpler structure. Since pressures on either side of the bulkhead will be typically closer to each other than to the ambient pressure outside the tank, the bulkhead can be made thinner than the outer vessel wall. The weight associated with two abutting domes and associated inter-tank structure may be largely eliminated. A tube or other extension of one chamber may pass through a second chamber so as to allow access to both fluids from one end of the common-bulkhead tank. This tube or extension may be an integral part of the bulkhead. Again, the internal bulkhead or bulkhead extension tube and tank wall may be mechanically uncoupled at one end, and a compliant liner or sealing member may be used at their juncture, allowing the two structures to deform or translate with respect to each other without leakage of internal fluid. Furthermore, the fluid-separating bulkhead and extension tube may also be configured as tank-integral, engine thrust structure.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.